Apparatus for cutting and stirring curd

ABSTRACT

Apparatus for cutting and stirring curd, comprising a curd vat with a shaft drivable for rotation, which shaft comprises a number of cutting frames extending radially from the shaft and having a number of strip-shaped transverse knives and longitudinal knives, the longitudinal knives each having an inner end situated near the shaft and an outer end situated near the wall of the curd vat, while at least a number of longitudinal knives of at least one of the cutting frames are provided, at the outer end situated near the wall of the curd vat, with a knife end section which has at least one portion extending transversely to the longitudinal direction of the longitudinal knives.

[0001] This invention relates to an apparatus for cutting and stirringcurd. Such apparatuses are known from practice and comprise a tank inwhich a rotatable shaft is situated which carries cutting framesextending radially from the shaft, which cutting frames are mounted onthe shaft in staggered relation. The cutting frames each comprise twospaced-apart parallel frame girders, which are mounted by one end on therotatable shaft and whose other end extends to a point near the wall ofthe tank. The tank can be disposed horizontally or vertically, therotatable shaft then being likewise horizontal or vertical.

[0002] Arranged between the frame girders is a lattice of longitudinaland transverse knives. The transverse knives extend transversely to theframe girders and are welded to them. The longitudinal knives extendparallel to the frame girders and are mounted on the transverse knivesby welding.

[0003] Such an apparatus is, for instance, the curd vat marketed byTetra Pak Tebel under the name of OST4. Such an apparatus is alsodescribed, for instance, in U.S. Pat. No. 4,108,058. A variant with twohorizontal shafts in a horizontal oval tank is described in U.S. Pat.No. 4,989,504.

[0004] All known apparatuses are arranged for stirring and cutting curdwhich has formed in the tank in that the tank has been filled with milkto which starter and rennet have been added. To that end, the centralshaft is driven for rotation, so that the cutting frames move throughthe curd formed. The cutting frames are usually designed such that theknives and the frame girders form a cutting edge along one edge and areblunt and rounded off along the other edge. Accordingly, rotation of thecentral shaft(s) in one direction substantially yields a cutting action,while rotation in the other direction substantially yields a stirringaction.

[0005] A problem occurring in the known apparatuses is that on the wallof the tank plaques of curd may form, which are not carried along by theknives of the cutting frames. Such plaques often come off the wall in alater stage, for instance during stirring, subsequent to cutting. If theplaques come off in such a late stage, comminution of the plaques takesplace too late, which has an adverse effect on the homogeneity of thecheese to be produced, since the point of cutting the curd is to promotemoisture egress. In the event of plaques or chunks undergoing a cuttingoperation later than the rest of the curd, moisture egress sustains adelay, which has a direct influence of the homogeneity of the cheese tobe produced.

[0006] The object of the invention is to obviate the problem outlinedand generally to make available a reliably and effectively workingapparatus for cutting and stirring curd, which enables the production ofa qualitatively superior-grade cheese.

[0007] According to the invention, an apparatus for cutting and stirringcurd, comprising a curd vat with a shaft drivable for rotation, whichshaft comprises a number of cutting frames extending radially from theshaft and having a number of strip-shaped transverse knives andlongitudinal knives, the longitudinal knives each having an inner endsituated near the shaft and an outer end situated near the wall of thecurd vat is characterized in that at least a number of longitudinalknives of at least one of the cutting frames are provided, at the outerend situated near the wall of the curd vat, with a knife end sectionwhich has at least one portion extending transversely to thelongitudinal direction of the longitudinal knives.

[0008] In the following, the invention will be further described withreference to the accompanying drawing.

[0009]FIG. 1 schematically shows in longitudinal cross section anexample of a known apparatus for cutting and stirring curd;

[0010]FIG. 2 schematically shows the apparatus of FIG. 1 in crosssection along the line II-II in FIG. 1;

[0011]FIG. 3 schematically shows in top plan view an example of a knowncutting frame for an apparatus for cutting and stirring curd; knives ofthe cutting frames. Such plaques often come off the wall in a laterstage, for instance during stirring, subsequent to cutting. If theplaques come off in such a late stage, comminution of the plaques takesplace too late, which has an adverse effect on the homogeneity of thecheese to be produced, since the point of cutting the curd is to promotemoisture egress. In the event of plaques or chunks undergoing a cuttingoperation later than the rest of the curd, moisture egress sustains adelay, which has a direct influence of the homogeneity of the cheese tobe produced.

[0012] The object of the invention is to obviate the problem outlinedand generally to make available a reliably and effectively workingapparatus for cutting and stirring curd, which enables the production ofa qualitatively superior-grade cheese.

[0013] According to the invention, an apparatus for cutting and stirringcurd, comprising a curd vat with a shaft drivable for rotation, whichshaft comprises a number of cutting frames extending radially from theshaft and having a number of strip-shaped transverse knives andlongitudinal knives, the longitudinal knives each having an inner endsituated near the shaft and an outer end situated near the wall of thecurd vat is characterized in that at least a number of longitudinalknives of at least one of the cutting frames are provided, at the outerend situated near the wall of the curd vat, with a knife end sectionwhich has at least one portion extending transversely to thelongitudinal direction of the longitudinal knives.

[0014] In the following, the invention will be further described withreference to the accompanying drawing.

[0015]FIG. 1 schematically shows in longitudinal cross section anexample of a known apparatus for cutting and stirring curd;

[0016]FIG. 2 schematically shows the apparatus of FIG. 1 in crosssection along the line II-II in FIG. 1;

[0017]FIG. 3 schematically shows in top plan view an example of a knowncutting frame for an apparatus for cutting and stirring curd;

[0018]FIG. 4 schematically shows an end view of the cutting frame ofFIG. 3;

[0019]FIG. 5 schematically shows a number of possible exemplaryembodiments of the invention; and

[0020]FIG. 6 schematically shows an example of a variant of one of theexamples of FIG. 5.

[0021]FIGS. 1 and 2 represent a known cylindrical horizontally-disposedcurd vat 1 which is supported by a number of legs 2. The end walls 3, 4of the curd vat 1 are conical in this example and through one of theseend walls a shaft 5 extends centrally into the curd container. Thisshaft, which in this example is journaled in the opposite end wall,supports a tool 6 for cutting and stirring curd in the curd container.Numeral 7 designates a sealing element between the shaft 5 and the wall3, through which the shaft 5 extends into the curd container.

[0022] Outside the curd container, the shaft 5 is connected by means ofa coupling 8 to a shaft 9, which is connected, in most cases coupleddirectly via transmission means 10, to a drive motor 11. The motor 11 isarranged for rotating the tool 6 around the centerline of the curd vat 1alternately in one direction and the other.

[0023] In this example, the curd vat 1 in its upper part has a manhole13 which is covered by a manhole cover 13 a. In this example, further,another opening is provided in the upper part of the curd container 1,which opening is designated by 14 and is intended for the immersion of awhey sieve 15 in the curd container 1. The whey sieve 15 in this exampleis supported by a bent pipe 16 which is rotatably connected to the curdcontainer 1 at 17. The curd vat 1 has an outlet 18 at its lowest part. Atriangle P indicates a customary level of the curd in the curd vat. Itis noted that the invention is also applicable to differently designedcurd vats.

[0024] The tool 6 comprises a number of cutting frames 19 which aresituated side by side along the shaft 5, as appears from FIG. 1. In theillustrated embodiment, the tool consists of six sections. The number ofsections depends on the size of the tank. The sections are connected tothe shaft, such that they form angles with each other, as can be seen inFIG. 2. In the illustrated embodiment, the sections are placed along theshaft 5 so as to extend outwards from the shaft in staggered relation.

[0025] Each of the sections may further be fitted at an angle to theshaft 5, as illustrated in FIG. 1 by a broken line 20 indicating thesection which is located farthest to the left and is concealed by theshaft 5.

[0026]FIGS. 3 and 4 schematically show in top plan view and end view anexample of a known cutting frame 19, as can be used, for instance, inthe apparatus of FIGS. 1 and 2. The known cutting frame comprises twoparallel frame girders 21, between which transverse knives 22 extendtransversely to the longitudinal girders 21, which transverse knives 22are welded to the frame girders. In turn extending transversely to thetransverse knives 22 and parallel to the frame girders are longitudinalknives 23, which are welded to the transverse knives. The longitudinalgirders, the transverse knives and the longitudinal knives are provided,on one longitudinal edge thereof, with a respective cutting edge 24, allsituated on the same side with respect to the cutting frame. The otherrespective longitudinal edge is blunt and typically of rounded design.The sharp edges serve for cutting the curd in one rotational directionof the shaft 5 and the blunt edges serve for stirring the curd in theother rotational direction.

[0027] It is noted that in FIG. 3 the longitudinal knives are longerthan the frame girders. In reality, however, the frame girders, at leaston the side of the rotatable shaft 5, whose centerline is indicated at27 in FIG. 3, either extend as far as the rotatable shaft or areconnected with the rotatable shaft through suitable extension piecesadapted, for instance, to receive the free ends of the frame girders.

[0028] At the end of the cutting frame 19 remote from the shaft, thelongitudinal knives terminate at a short distance d₁ from the shell ofthe tank 1. A plaque forming on the inside surface of the shell of thetank, if such plaque has a thickness greater than the dimension d₁, willtherefore be cut by the ends of the knives 23 following parallel cuttinglines. In-between the knives, however, the plaque can have a greaterthickness than the dimension d₁. Eventually, the thickness of the plaquewill increase to such an extent that, through the combined action of theterminal end faces of the longitudinal knives and the side surface ofthe longitudinal knives contiguous to the terminal end faces, the plaquewill be pulled off the tank wall. After that, the loosened plaques canbe further comminuted by the rotary cutting frames.

[0029] An example of such a curd plaque accretion is designated in FIG.3 by 26. The plaque 26 has an uncut base portion of a thickness d₁, anda portion of a thickness d₂ which has been cut by the straight ends ofthe knives 23. In FIG. 3, the lateral distance between the knives andthe material of the plaque is represented exaggeratedly. In the plaque,moisture egress proceeds differently than in the remainder of the curdin the tank. This difference is not fully compensated anymore after theplaque has come off the tank wall. Cheeses into which parts of suchplaques have been incorporated are less homogeneous than cheesesobtained from curd from a tank in which such plaques do not occur.

[0030] According to the invention, the formation of plaques of curdagainst the wall of a curd vat is prevented, or at least reduced, byproviding the ends of the longitudinal knives with special knife ends,which comprise at least one portion extending substantially transverselyto the longitudinal knives.

[0031]FIG. 5 shows a part of a tank wall 25, as well as a number ofexamples of ends of longitudinal knives 23 a to 23 j extendingtransversely to the tank wall and terminating adjacent the tank wall.All ends are provided with special knife end sections having partsextending transversely to the knife direction. The longitudinal knives23 a and 23 b are provided with knife end sections 30 being T-shaped intop plan view, which have been obtained either by attaching a T-shapedpart to the end of the longitudinal knives or by simply forming atransverse portion. Attachment can be done, for instance, throughwelding. By way of alternative (not shown), it is possible to fit asingle continuous transverse strip on the ends of a number oflongitudinal knives located next to each other.

[0032] The knives 23 c and 23 d are provided with a shared U-shaped part31 of a somewhat round shape. The knives 23 e and 23 f are provided witha shared U-shaped part 32 of a more angular shape. The knives 23 g and23 h are each provided with an arcuate transverse part 33, whilst thelongitudinal knives 23 i and 23 j are provided with crosspieces 34situated on one side of the longitudinal knives.

[0033] Although it is possible, in principle, to employ different knifeends in one and the same cutting frame, normally a single type of knifeend will be used in one cutting frame, and probably also in one curdvat. The knife ends can be provided directly during the manufacture of acutting frame and, depending on the selected type, may then beintegrally formed with the longitudinal knives. This applies, forinstance, to the knife ends 34 which can be readily obtained by bendingover the ends of the respective longitudinal knives. However, the knifeends can also be discrete elements which are suitably attached to thelongitudinal knives, for instance through welding. Such discreteelements have as a great advantage that with the aid thereof existingcutting frames can be easily converted.

[0034] It is noted that after the foregoing, various modifications willreadily occur to those skilled in the art. Thus, if desired, thelongitudinal knives can also be provided with the above-described knifeends at the inner end thereof, i.e., the end situated proximal to theshaft 5. It is also possible for the end elements to be fitted so as tobe slightly staggered upwards or downwards, viewed in the direction ofmovement of the longitudinal knives, as is shown in FIG. 6. FIG. 6 showsthe end face of a longitudinal knife 23 on which a transverse endelement 35 has been fitted, displaced slightly upwards. Also indicatedin FIG. 6 is that, if desired, a second end element 36 may be used,which is arranged in a downwardly displaced position. These and similarmodifications are understood to fall within the framework of theinvention.

1. An apparatus for cutting and stirring curd, comprising a curd vat with a shaft drivable for rotation, which shaft comprises a number of cutting frames extending radially from the shaft and having a number of strip-shaped transverse knives and longitudinal knives, the longitudinal knives each having an inner end situated near the shaft and an outer end situated near the wall of the curd vat, characterized in that at least a number of longitudinal knives of at least one of the cutting frames are provided, at the outer end situated near the wall of the curd vat, with a knife end section which has at least one portion extending transversely to the longitudinal direction of the longitudinal knives.
 2. An apparatus according to claim 1, characterized in that the knife end section is substantially T-shaped in top plan view.
 3. An apparatus according to claim 1, characterized in that the knife end section is substantially U-shaped in top plan view.
 4. An apparatus according to claim 1, characterized in that the knife end section is substantially L-shaped in top plan view.
 5. An apparatus according to claim 1, characterized in that the knife end section is substantially arcuate in top plan view.
 6. An apparatus according to any one of the preceding claims, characterized in that two or more adjacent longitudinal knives have knife end sections having a common portion extending transversely to the longitudinal direction of the longitudinal knives.
 7. An apparatus according to any one of the preceding claims, characterized by at least one longitudinal knife having a transverse portion which is arranged in an upwardly and/or downwardly displaced position with respect to the longitudinal axis of the longitudinal knife.
 8. An apparatus according to any one of the preceding claims, characterized in that the knife end sections are discrete elements which are attached to the ends of the longitudinal knives.
 9. A cutting frame for an apparatus according to any one of the preceding claims, comprising longitudinal knives and transverse knives, characterized in that at least a number of longitudinal knives are provided at one of the ends with a knife end section having at least one portion extending transversely to the longitudinal direction of the longitudinal knives.
 10. A cutting frame according to claim 9, characterized by one or more knife end sections as described in any one of claims 2 to
 8. 11. A loose knife end section element suitable for use on ends of longitudinal knives of an apparatus according to any one of claims 1 to 8 or of a cutting frame according to claim 9 or
 10. 